Turns out there existed a problem with the save system in the game. Due to increased functionality to map building via the Map Editor, the saves haven't been working properly.
However, this issue is now resolved and it is again possible to save/load in singleplayer and hotseat modes.

In addition to that, a few other updates made it into the game and editor:
- all maps have been updated and are included with the game (they will no longer show as outdated);
- Map Editor has been updated to included our 3 latest piece: Tavern, Siege Tower, and Trebuchet;
- minor UI fixes.